Cork composition manufacture



Uited States Patent CORK C ZBMPGSITION MANUFACTURE Washington H. Phillips, Lancaster, Pa., assignor to Armstrong Qork Company, Lancaster, Pa., a corporation of Pennsylvania No Drawin Application May 20, 1952, Serial No. 239,ti00

1i Claims. (Cl. 106-127) This invention relates to the manufacture of cork composition and is concerned particularly with the production of gelatine glue-bound cork compositions having the binder uniformly distributed over the cork granules without the use of large quantities of water normally required for dispersion or dilution of the binder, the compositions having incorporated therein a severing aid such as a nondrying hydrocarbon oil, the presence of which increases the wet shear strength or apparent viscosity of the binder and aggravates the mixing problem.

in the manufacture of cork compositions utilizing a glue binder, common practice is to form a mixture of glue and water, generally with the addition of a material such as glycerine, triethylene glycol, sorbitol, and mixtures thereof which serves to maintain the composition in a softened condition. The binder is distributed over the cork granules in a mixer; and in order to secure a uniform distribution of the binder over the cork granules, the viscosity of the binder is reduced by mild heating and the incorporation of additional Water. Where the cork is ground into granules of relatively small size, common practice is to reduce substantially the viscosity of the binder by the addition of a relatively large volume of water in order to avoid'the formation of agglomerates consisting of cork particles rich in binder coating, such agglomerates appearing irregularly throughout the mass. Such binder-rich agglomerates have been referred to in the industry as glue balls. When substatnial volumes of water are employed to secure a uniform distribution of the binder over the cork granules, it is necessary in most instances to dry the coated granules by blowingheated air through the mass to drive off a portion of the water before baking is effected. if this drying is not accomplished, an excessively long mold dwell time is required subsequent to the baking of the mass of binder-coated granules, since the high vapor pressure of a the binder retards the stress relaxation and setting of the cork granules. This problem is discussed in Gard Patent No. 2,601,702. Also, the use of large volumes of water is objectionable for the reason that at least some of the Water will remain in the mass after curing a I' of the binder. This water gradually evaporates from the composition, particularly after severance into sheets, and results in shrinkage of the composition. Where dimensional stability is necessary, as in gasket manufacture, this shrinkage may be a major problem.

It has been suggested heretofore to incorporate a a nondrying hydrocarbon oil in cork compositions to serve as an aid in the severance of the finished product. Cork compositions are frequently used in the fabrication of sheets for gaskets, and these sheets are obtained by the severance of a mold-formed mat, which may be three or more inches thick, into sheets of 1 inch or other desired thicknesses for gasket service. As is well known, cork is a diflicult material to sever,

and by the incorporation of the oil the severing operation is facilitated. It has been found, however, that when effective amounts of oils are added to a glue binder for cork composition, the wet shear strength or apparent 'viscosity increases substantially, and it is virtually impossibleto obtain a uniform distribution of the binder;

over the granules of cork without objectionable binder dilution. This problem is not restricted entirely to compositions made from relatively small-sized cork granules,

but exists as well- -however to a somewhat lesser .deg gree-in. compositions made fromnlargersrzed cork 2,698,253 Patented Dec. 28, 1954 granules. When high-speed mixing tackle is used, excessive burning of the binder occurs at high shear points in the mixer. Some of this burned binder is attached to projections on the mixer; and these burned binder masses glaze over, break off eventually, and appear as brown spots of degraded binder in the finished cork composition product. This problem may be minimized by the addition of relatively large volumes of water to the binder; but, as mentioned above, this addition in turn results in an excessive mold dwell period and aggravates the problem of maintaining dimensional stability. The burning at the high shear points may be reduced by cooling the mixer, but this action is ob; jectionable in that it is desirable tocharge the bindercoated cork granules into the molds for baking atas high a temperature as reasonably possible; for, otherwise, additional heating in the mold over that ordinarily required would be necessary. In addition, cooling of the mixer will increase somewhat the viscosity of the binder, thus aggravating the binder build-up and subsequent burning at points of high shear. The increase in apparent viscosity is so great when a mineral oil severing aid is added to the ordinary glue binder that the cork granules and binder form a taffylike mass which is not free flowing; consequently, metering, goplpering, and mold charging become extremely difcut.

One object of this invention, therefore, is to overcome the problem of the increase in wet shear strength or apparent viscosity of a glue binder for cork compositions which is brought about by the incorporation of a nondrying hydrocarbon oil severing aid in the composition.

Another object of this invention is to provide a method of making cork compositions utilizing a glue binder and a nondrying hydrocarbon oil severing aid in which the distribution of the binder over the cork granules is effected without objectionable dilution of the glue by use of excessive amounts of water.

According to this invention a cork composition is prepared from a major portion by volume of cork granules and a binder comprising the heat-activated product of a mixture of glue, a nondrying hydrocarbon oil severing aid, Water, and an insolubilizing agent for the glue. A small but effective amount of a non-ionic surface active material is added to the mixture which combines with the water and the mineral oil probably to form an emulsion or dispersion of the mineral oil in the water which reduces the wet shear strength or apparent viscosity of the binder and facilitates its distribution over the cork granules. The exact chemical action which occurs, if any, is not known. It is believed that the reaction is essentially a physical one, for the binding value of the glue does not appear to be affected. In any event, it is possible to distribute the binder over the cork" granules with facility even with as much as 15 parts by weight of oil for each parts by weight of cork granules and 6.5 parts of glue, with but a minor amount of water, and mixing may be effected without burning of the binder when high-speed mixing tackle is employed.

The following is an example of a cork composition made in accordance with the invention.

Parts by weight .2 lnsolubilizing agent (paraformaldehyde) .52

In the above example gelatine glue is the principal binding component. A bone or hide glue or mixtures thereof may be used. Peter Coopers No. 2994 Glue, a bone glue, is commonly used in cork composition manufacture. Part or all of the glycerine maybe replaced by triethylene' glycol, sorbitol, or mixtures of such materials. -They are preferably incorporated di- 0 .Iectly in the binder, although they may be distributed over the. cork granules pr or; to the incqrporation of the binder, for the prime purpose of such materials is to maintain the composition in a softened condition. The oil may be a paraffin base mineral oil which is substantially neutral in acidity, having an aniline point be low 80 C. and a viscosity in the order of 75 to 100 Saybolt. Tycol No. 110 mineral oil sold by Tidewater Oil Company meets these specifications. Any nondrying hydrocarbon oil severing aid may be used. The paraffinic mineral oils are preferred. The non-ionic surface active material may be essentially a partial ester of a common fatty acid or acids such as lauric, palmitic, stearic, and oleic; and hexitol anhydrides (bexitans and hexides) derived from sorbitol. Or the agent may be a material derived from one or more of the foregoing products by adding polyoxyethylene chains to the nonesterified hydroxyls. Such products are sold by Atlas Powder Company under the trade names Span and Tween, respectively. Preferably a mixture of both types is employed, using about one half of each. In the above example the mixture may comprise .125 part by weight of Tween and .125 by weight of Span 20. Other non-ionic surface active materials may be substituted. Paraformaldehyde is the preferred insolubilizing agent, but other aldehyde-yielding substances or mixtures thereof may be used, as is well known in the art.

In the manufacture of a cork composition in accordance with the above example, the glue, glycerine, oil, non-ionic surface active material, and water are mixe together. Heating is effected during mixing of the ingredients, with the batch as finally prepared having a temperature in the order of 195 F. The heated binder is then charged onto the cork granules and distributed uniformly thereover. This distribution may be effected in any one of a number of mixing devices including the modern high-speed mixer such as the Sprout-Waldron Super Duty De Luxe Coldmix High Speed Agitator manufactured by Sprout-Waldron Company of Muncy, Pennsylvania.

The binder of the foregoing example has a much lower wet shear strength than the same binder without the nonionic surface active material. This reduction in wet shear strength may be determined by testing the binders with a conventional Brookfield viscometer. In a test made on the composition of the above example with a Brookfield viscometer operating at 190 to 195 F. with spindle No. 3 rotating at 20 R. P. M. the viscosity was determined to be 1180. The same binder without the non-ionic surface active material was similarly tested and was found to have a viscosity of 4000. This reduction in wet shear strength or apparent viscosity makes it possible to distribute the binder uniformly over the cork granules. The identical binder of the above example without the non-ionic surface active material could not be successfully distributed over the cork granules, for glue balls would inevitably occur; and if a high-speed mixer were employed without cooling, heat degradation of the binder at the points of high shear would result.

While preferred practice is to mix the glue, glycerine, oil, water, and non-ionic surface active material together and then to distribute the mixture overthe cork granules, other procedures may be followed. For instance, the cork granules may be pretreated with the oil or a mixture of the oil and glycerine, and the other binder ingredients may be added subsequently. Another procedure would be to coat the cork granules with the mixed binder, except for the oil, by delivering streams of the binder onto a flowing mass of cork granules, as disclosed in my application Serial No. 196,135, filed November 17, 1950, and entitled Method and Apparatus for Making Cork Compositions and the like, and then to add the oil onto the binder-carrying mass of cork particles, discharging the same into a continuous mixer, such as the Sprout-Waldron mixer referred to above, and to accomplish final and uniform distribution of all of the binder ingredients over the cork granules in the continuous mixer.

The problem of reducing the wet shear strength or apparent viscosity of the binder is present in all of the foregoing procedures. It appears that, upon bringing the glue, water, and oil together, an increase in viscosity occurs, regardless of whether the oil is mixed with the other binder ingredients, is applied to the cork granules prior to the addition of the other binder ingredients, or is added on the side to granules partially precoated with the other binder ingredients. The addition of the nonionic surface active material to the glue and water aids in dispersion of the glue; and for that reason, it is preferred to combine these ingredients, whether the oil be added directly thereto to form the complete binder or the oil be otherwise incorporated into the composition.

The severing aid may be incorporated in the range of l to 15 parts by weight for each parts by weight of cork. The quantity of water incorporated should be maintained as low as possible to keep the vapor pressure of the binder to as low a value as obtainable because of the effect it has on the mold dwell time and to minimize shrinkage of the final product, as previously mentioned. Generally, about 30 to 45 parts by weight of water for each 100 parts by weight of glue will be found satisfactory. There must be water present to obtain the desired action of the non-ionic surface active material. The quantity of non-ionic surface active material incorporated will vary, depending upon the particular surface active material or materials employed, the quantity of oil which is added to the composition, the viscosity of the oil, the increase in viscosity or wet shear strength which the oil imparts to the particular glue employed, and other variable factors. A quantity in the order of 3 to 5 parts by weight of non-ionic surface active material for each 100 parts by weight of oil will generally be found acceptable for reducing the wet shear strength of the binder to a point where the binder may be distributed over the cork granules without the formation of objectionable glue balls or burned binder streaks, with the quantity of water being maintained at a relatively low value, in the order of 30 to 45 parts by weight for each 100 parts by weight of glue. It has been observed that when quantities of non-ionic surface active material in excess of about 5 parts by weight for each 100 parts by weight of oil are incorporated, no substantial improvement in the reduction in wet shear strength or apparent viscosity is obtained. Since these materials are rather expensive, it is preferred, of course, to limit the quantities incorporated. The addition of an excessive amount of non-ionic surface active material within reasonable limits, up to about 10% of the weight of the oil, does not appear to deleteriously affect the quality of the cork composition. When quantities lower than about are employed, adequate reduction in wet shear strength or apparent viscosity is not obtained.

While the invention finds particular usefulness in compositions which include a material which maintains the composition in a softened condition, such as glycerine and triethylene glycol, the invention will also be useful in compositions where no such material is incorporated. Such compositions are used in the manufacture of cork cigarette tipping materials, for instance.

Care should be exercised to avoid the use of any materials in the composition which will deleteriously affect the glue. Cationic and anionic surface active materials should be avoided for they are not the equivalent of the non-ionic materials and have been found to adversely affect the binding value of glue.

I claim:

1. A cork composition comprising cork granules and a binder therefor, said binder comprising the heat-activated product of a mixture of gelatine glue, a nondrying hydrocarbon oil severing aid, /2 to 10 parts by weight for each 100 parts by weight of oil of a non-ionic surface active material which reduces the wet shear strength of thebinder, water, and an insolubilizing agent for the g ue.

2. A cork composition comprising a major portion by volume of cork granules and a binder therefor comprising the heat-activated product of a mixture of gelatine glue, 1 to 15 parts by weight of a nondrying hydrocarbon oil severing aid for each 100 parts by weight of cork, /2 to 10 parts by weight for each 100 parts by weight of oil of a non-ionic surface active material which reduces the wet shear strength of the binder, 30 to 45 parts by weight of water for each 100 parts by weight of glue, and sufficient insolubilizing agent to react with substantially all of the glue.

3. A cork composition in accordance with claim 2 in WiflliCh the nondrying hydrocarbon oil is a neutral mineral o 4. A cork composition in accordance with claim 2 in which the nondrying hydrocarbon oil is a neutral paratfinic mineral oil.

5. A cork composition comprising a major portion by volume of cork granules and a binder therefor comprising the heat-activated product of a mixture of gelatine glue, 1 to 15 parts by weight of a nondrying hydrocarbon oil severing aid for each 100 parts by weight of cork, at least 3 parts by weight for each 100 parts by weight of oil of a non-ionic surface active material which reduces the wet shear strength of the binder, water, and sufficient insolubilizing agent to react with substantially all of the g ue.

6. In a method of making cork composition in which cork granules are coated with a binder comprising gelatine glue, a nondrying hydrocarbon oil severing aid which increases the wet shear strength of the binder, water, and an insolubilizing agent for the glue, the improvement which consists in adding to the binder from V2 to parts by weight for each 100 parts by weight of oil of a non-ionic surface active material which reduces the wet shear strength of the binder and facilitates its distribution over the cork granules.

7. In a method of making cork composition in which a major portion by volume of cork granules is coated with a binder comprising gelatine glue, water, and an insolubilizing agent for the glue, the improvement which consists in adding to the binder from 1 to parts by weight for each 100 parts by weight of cork of a nondrying hydrocarbon oil severing aid and from to 10 parts by weight for each 100 parts by weight of oil of a non-ionic surface active material which reduces the wet shear strength of the glue and oil mixture and facilitates its distribution over the cork granules.

8. In a method of making cork composition in which a major portion by volume of cork granules is coated with a binder comprising gelatine glue, water, and an insolubilizing agent for the glue, the improvement which consists in adding to the binder from 1 to 15 parts by weight for each 100 parts by weight of glue of a neutral mineral oil severing aid and from A to 10 parts by weight for each 100 parts by weight of oil of a nonionic surface active material which reduces the wet shear strength of the glue and oil mixture and facilitates its distribution over the cork granules.

9. A cork composition consisting essentially of cork granules and a binder therefor, said binder comprising the heat-activated product of a mixture of gelatine glue, 1 to 15 parts by weight of a nondrying hydrocarbon oil severing aid for each 100 parts by weight of cork, 3 to 5 parts by weight for each 100 parts by weight of oil of a nonionic surface active material which reduces the wet shear strength of the binder, and 30 to parts by weight of water for each parts by weight of glue.

10. In a method of making cork composition which consists essentially of cork granules and a gelatine glue binder therefor, the improvement which consists in incorporating in the composition 30 to 45 parts by weight of water for each 100 parts by weight of glue, 1 to 15 parts by weight for each 100 parts by Weight of cork of a nondrying hydrocarbon oil severing aid, and from 3 to 5 parts by Weight for each 100 parts by weight of oil of a non-ionic surface active material which reduces the wet shear strength of the glue, water, and oil mixture and facilitates its distribution over the cork granules.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,104,692 Cooke et al. Jan. 4, 1938 2,237,753 Dangelmajer Apr. 8, 1941 2,383,096 Warth et al Aug. 21, 1945 OTHER REFERENCES Atlas Surface Active Agents, Atlas Powder C0,, 1948, page 38. 

1. A CORK COMPOSITION COMPRISING CORK GRANULES AND A BINDER THEREFOR, SAID BINDER COMPRISING THE HEAT-ACTIVATED PRODUCT OF A MIXTURE OF GELATINE GLUE, A NONDRYING HYDROCARBON OIL SEVERING AID, 1/2 TO 10 PARTS BY WEIGHT FOR EACH 100 PARTS BY WEIGHT OF OIL OF A NON-IONIC SURFACE ACTIVE MATERIAL WHICH REDUCES THE WET SHEAR STRENGTH OF THE BINDER, WATER, AND AN INSOLUBILIZING AGENT FOR THE GLUE. 